Light emitting module and lens

ABSTRACT

A lens including an upper surface having a curved portion having a changing curvature in a direction extending away from a central axis of the lens, and a lower surface having a concave portion disposed on the central axis of the lens. The concave portion of the lower surface includes an entrance disposed on a lower region of the concave portion and configured to receive light emitted from a light-emitting diode chip, and an upper end surface disposed on an upper region of the concave portion. The concave portion includes a width that narrows in a direction extending away from the entrance. The upper end surface is nonplanar.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/585,791, filed on Dec. 30, 2014, which is a continuation of U.S.patent application Ser. No. 14/362,393, filed on Jun. 2, 2014, which isthe National Stage Entry of International Application No.PCT/KR2012/010314, filed on Nov. 30, 2012, and claims priority from andthe benefit of Korean Patent Application No. 10-2011-0128375, filed onDec. 2, 2011, and Korean Patent Application No. 10-2011-0141098, filedon Dec. 23, 2011, which are hereby incorporated by reference for allpurposes as if fully set forth herein.

BACKGROUND Field

The present invention relates to a light emitting module, and moreparticularly, to a light emitting module including a lens for use as asurface illumination or a backlight of a liquid crystal display.

Discussion of the Background

There are edge-type backlights and direct-type backlights forbacklighting a liquid crystal display. As for the edge-type backlights,light emitting diodes (LEDs) are arranged on a side of a light guideplate, and light incident from a light source backlights a liquidcrystal panel by using the light guide plate. The edge-type backlightscan reduce the number of LEDs and does not require a high level ofquality deviation among LEDs. Therefore, the edge-type backlights arecost-effective and are advantageous to development of low powerconsuming products. However, the edge-type backlights can hardlyovercome a difference in contrast between an edge portion and a centralportion of the liquid crystal display, and has a limitation inimplementing high picture quality.

On the other hand, as for the direct-type backlights, a plurality ofLEDs are arranged directly under a liquid crystal panel at constantintervals, and light from the LEDs backlights the liquid crystal panel.The direct-type backlights have advantages that can overcome adifference in contrast between an edge portion and a central portion ofthe liquid crystal panel and can implement high picture quality.

However, in the case of the direct-type backlights, if the respectiveLEDs cannot uniformly backlight a relatively large area, it is necessaryto densely arrange a larger number of LEDs, resulting in an increase inpower consumption. In addition, if the LEDs have quality deviation, theliquid crystal panel is non-uniformly backlighted, making it difficultto secure uniform quality of a screen.

In order to reduce the number of LEDs used, technique for dispersinglight by arranging a lens in each LED may be used. However, even aslight change in alignment between the LED and the lens may cause aserious change in distribution of light emitted through the lens, makingit more difficult to uniformly backlight the liquid crystal panel.

Also, as illustrated in FIG. 1, when a lens having a disk-shaped lightorientation pattern LP is applied, a bright portion WP in which adjacentlight beams cross each other and a dark portion BP in which light israrely irradiated may be formed.

The bright portion WP can be controlled by reducing luminous fluxtravelling toward the bright portion WP, while adjusting brightnessbased on an viewing angle of the light orientation pattern LP. On theother hand, the dark portion BP can be controlled by increasing the sizeof the light orientation pattern LP or reducing a gap between the LEDs.However, if the luminous flux travelling toward the bright portion WP isreduced so as to remove the bright portion WP, the dark portion BP mayfurther darken, and conversely, if the size of the light orientationpattern LP is increased or the gap between the LEDs is reduced so as toremove the dark portion BP, the bright portion WP becomes wider andbrighter. In other words, it is difficult to remove both the brightportion WP and the dark portion BP.

SUMMARY

An aspect of the present invention is directed to a lens for dispersinglight and a light emitting module including the same, and moreparticularly, to a light emitting module and a lens suitable for asurface light source or a direct-type backlight source.

Another aspect of the present invention is directed to a lens fordispersing light and a light emitting module including the same, andmore particularly, to a lens and a light emitting module capable ofincreasing an alignment tolerance between an LED and a lens.

Another aspect of the present invention is directed to a light emittingmodule and a lens capable of emitting uniform light over a large area ina light source using a plurality of LEDs.

Another aspect of the present invention is directed to a lens and alight emitting module that are easy to fabricate.

According to an aspect of the present invention, a light emitting moduleincludes a light emitting diode chip, and a lens dispersing luminousflux of light emitted from the light emitting diode chip. The lensincludes: a lower surface having a concave portion on which lightemitted from the light emitting diode chip is incident; and an uppersurface from which the light incident on the concave portion is emitted.The upper surface includes a concave surface positioned in a centralaxis thereof. The concave portion of the lower surface includes at leastone of a surface perpendicular to the central axis and a downwardlyconvex surface. At least one of the surface perpendicular to the centralaxis and the downwardly convex surface is positioned within a regionnarrower than an entrance region of the concave portion.

The upper surface and the concave portion of the lens may have a mirrorsurface symmetry with respect to a surface passing through the centralaxis. The upper surface and the concave portion of the lens may have arotator shape with respect to the central axis.

The upper surface of the lens may include a convex surface continuouslyextending from the concave surface.

In some embodiments, light scattering patterns may be formed on at leastone of the surface perpendicular to the central axis and the downwardlyconvex surface within the concave portion of the lower surface and on asurface positioned closer to the central axis than the at least onesurface. A light scattering pattern may be formed with an unevenpattern, and may further disperse light emitted from the light emittingdiode to the vicinity of the central axis.

A light scattering pattern may be formed on the concave surface of theupper surface.

In some embodiments, material layers having a refractive index differentfrom the lens may be further formed on at least one of the surfaceperpendicular to the central axis and the downwardly convex surfacewithin the concave portion of the lower surface and on a surfacepositioned closer to the central axis than the at least one surface.

A material layer having a refractive index different from the lens maybe further formed on the concave surface of the upper surface.

At least one of the surface perpendicular to the central axis and thedownwardly convex surface is limitedly positioned in a region narrowerthan a region surrounded by inflection lines where the concave surfaceand the convex surface of the upper surface meet each other. At leastone of the surface perpendicular to the central axis and the downwardlyconvex surface is limitedly positioned in a region narrower than a lightexit surface region of the light emitting device.

The lens may further include a flange connecting the upper surface andthe lower surface, and at least one of the surface perpendicular to thecentral axis and the downwardly convex surface within the concaveportion is positioned above the flange.

In some embodiments, the light emitting module may include a lightemitting device, wherein the light emitting device includes: the lightemitting diode chip; a housing in which the light emitting diode chip ismounted; and a wavelength conversion layer converting a wavelength oflight emitted from the light emitting diode chip. The wavelengthconversion layer may be spaced apart from the concave portion of thelens and positioned under the lens.

The light emitting module may further include a printed circuit board inwhich the light emitting device is mounted, and the lens may be placedon the printed circuit board. For example, the lens may have legs, andthe legs of the lens may be placed on the printed circuit board.

Air gap may exist between the light emitting device and the concaveportion. Therefore, the light incident on the concave portion may beprimarily refracted from the surface of the concave portion.

According to another aspect of the present invention, a lens includes alight emitting diode chip, and a lens dispersing luminous flux of lightemitted from the light emitting diode chip. The lens includes: a lowersurface having a concave portion on which light emitted from the lightemitting diode chip is incident; and an upper surface from which thelight incident on the concave portion is emitted. An entrance region ofthe concave portion has a shape elongated in a single axis direction.

The entrance region of the concave portion may have various shapes. Forexample, the entrance region of the concave portion may have arectangular shape, an oval shape, or a rectangular shape with roundedcorners.

A cross-sectional shape of the concave portion along the single axisdirection may be a trapezoid shape in which the concave portion issymmetrical with respect to a central axis and a lateral surface is astraight line, or a trapezoid shape in which the lateral surface is acurved line. Also, a cross-sectional shape of the concave portion alonga direction perpendicular to the single axis direction may be atrapezoid shape in which the concave portion is symmetrical with respectto the central axis and a lateral surface is a straight line, or atrapezoid shape in which the lateral surface is a curved line.

The upper portion of the lens may have a rotational symmetry, but is notlimited thereto. The upper portion of the lens may have a shapeelongated in a direction perpendicular to the single axis direction. Theupper surface may have a shape in which two hemispheres overlap eachother.

In some embodiments, the upper surface may include a concave surfacepositioned in a central axis thereof. The concave portion of the lowersurface may include at least one of a surface perpendicular to thecentral axis and a downwardly convex surface. At least one of thesurface perpendicular to the central axis and the downwardly convexsurface may be positioned in a region narrower than an entrance regionof the concave portion.

The upper surface and the concave portion of the lens may have a mirrorsurface symmetry with respect to a surface passing through the centralaxis.

The upper surface of the lens may include a convex surface continuouslyextending from the concave surface.

In some embodiments, light scattering patterns may be formed on at leastone of the surface perpendicular to the central axis and the downwardlyconvex surface within the concave portion of the lower surface and on asurface positioned closer to the central axis than the at least onesurface. A light scattering pattern may be formed with an unevenpattern, and may further disperse light emitted from the light emittingdiode to the vicinity of the central axis.

Alight scattering pattern may be formed on the concave surface of theupper surface.

The lens may further include a flange connecting the upper surface andthe lower surface. At least one of the surface perpendicular to thecentral axis and the downwardly convex surface within the concaveportion may be positioned above the flange.

In some embodiments, the light emitting module may further include alight emitting device, wherein the light emitting device includes: thelight emitting diode chip; a housing in which the light emitting diodechip is mounted; and a wavelength conversion layer converting awavelength of light emitted from the light emitting diode chip. Thewavelength conversion layer may be spaced apart from the concave portionof the lens and positioned under the lens.

The light emitting module may further include a printed circuit board inwhich the light emitting device is mounted, and the lens may be placedon the printed circuit board. For example, the lens may include legs,and the legs may be placed on the printed circuit board.

Air gap may exist between the light emitting device and the concaveportion. Therefore, the light incident on the concave portion may beprimarily refracted from the surface of the concave portion.

According to embodiments of the present invention, since primaryrefraction occurs in a concave portion of a lens and secondaryrefraction occurs in an upper surface of the lens, the lens canextensively disperse light. In addition, since an upper end of theconcave portion of the lens is shaped to include a flat surface or aconvex surface, instead of a concave surface, an alignment tolerancebetween an LED chip or a light emitting device and the lens can beincreased. Furthermore, since a change in light orientation distributioncharacteristics according to the shape of the upper end of the concaveportion of the lens can be alleviated, a lens fabrication process marginis increased, making it easy to fabricate the lens.

Also, since an entrance region of the concave portion of the lens, onwhich light is incident, has an elongated shape, light can beextensively dispersed in a minor-axis direction, thereby implementing anelongated light orientation pattern. Thus, by arranging a plurality ofLED chips and arranging the lens on each of the LED chips, luminous fluxcan be uniformly distributed over a large area by the elongated lightpatterns, thereby implementing a uniform surface light source.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a view for describing a light pattern of a surface lightsource according to the related art.

FIG. 2 is a schematic cross-sectional view for describing a lightemitting module according to an embodiment of the present invention.

FIG. 3 is a schematic perspective view for describing a light emittingdevice.

FIGS. 4(a) to (d) are cross-sectional views for describing variousmodifications of a lens.

FIGS. 5(a) and (b) are lens cross-sectional views for describing a lightemitting module according to another embodiment of the presentinvention.

FIG. 6 is a cross-sectional view for describing dimensions of a lightemitting module used in a simulation.

FIGS. 7(a) to (c) are graphs for describing shapes of the lens of FIG.6.

FIG. 8 is a view illustrating a light beam travelling direction of thelens of FIG. 6.

FIGS. 9(a) and (b) are graphs showing illuminance distributions.Specifically, FIG. 9A shows an illuminance distribution of a lightemitting device, and FIG. 9B shows an illuminance distribution of alight emitting module using a lens.

FIGS. 10(a) and (b) are graphs showing light orientation distributions.Specifically, FIG. 10A shows a light orientation distribution of a lightemitting device, and FIG. 10B shows a light orientation distribution ofa light emitting module using a lens.

FIG. 11 is a view for describing a light pattern of a surface lightsource according to other embodiments of the present invention.

FIG. 12 is a schematic perspective view of a light emitting moduleaccording to an embodiment of the present invention.

FIGS. 13(a) and (b) are cross-sectional views of the light emittingmodule of FIG. 12, taken along x-axis and y-axis.

FIG. 14 is plan views for describing various shapes of a concave portionof a lens.

FIGS. 15(a) and (b) and 16(a) and (b) are cross-sectional views fordescribing various shapes of the concave portion of the lens.

FIG. 17 is a graph for describing a light orientation distribution ofthe light emitting module according to the present invention.

FIGS. 18(a) to (c) are a perspective view and cross-sectional views fordescribing a lens according to another embodiment of the presentinvention.

FIG. 19 is a cross-sectional view for describing a light emitting moduleincluding a plurality of light emitting devices according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Exemplary embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the present invention tothose skilled in the art. Throughout the disclosure, like referencenumerals refer to like elements throughout this disclosure.

FIG. 2 is a schematic cross-sectional view for describing a lightemitting module according to an embodiment of the present invention, andFIG. 3 is a perspective view for describing a light emitting device usedin the light emitting module.

Referring to FIG. 2, the light emitting module includes a printedcircuit board (PCB) 10, a light emitting device 20, and a lens 30.Although the PCB 10 is partially illustrated, a plurality of lightemitting devices 20 may be variously arranged in a matrix form, ahoneycomb form, or the like, on the single PCB 10.

The PCB 10 includes conductive land patterns, which are to be bonded toterminals of the light emitting device 20, on an upper surface thereof.Also, the PCB 10 may include a reflective film on the upper surfacethereof. The PCB 10 may be a metal-core PCB (MCPCB) based on a metalhaving excellent thermal conductivity. Also, the PCB 10 may be based onan insulating substrate material such as FR4. Although not illustrated,a heat sink may be disposed under the PCB 10 in order to dissipate heatgenerated from the light emitting device 20.

As illustrated in FIG. 3, the light emitting device 20 includes ahousing 21, an LED chip 23 mounted on the housing 21, and a wavelengthconversion layer 25 covering the LED chip 23. The light emitting device20 further includes lead terminals (not illustrated) supported by thehousing 21.

The housing 21 constituting a package body may be formed byinjection-molding a plastic resin, such as PA or PPA. In this case, thehousing 21 may be molded in a state of supporting the lead terminalsthrough the injection molding process, and may have a cavity 21 aallowing the LED chip 23 to be mounted therein. The cavity 21 a definesa light exit region of the light emitting device 20.

The lead terminals are disposed to be spaced apart from each otherwithin the housing 21, and extend to the outside of the housing 21, suchthat the lead terminals are bonded to the land patterns on the PCB 10.

The LED chip 23 is mounted on the bottom of the cavity 21 a andelectrically connected to the lead terminals. The LED chip 23 may be agallium nitride-based LED that emits ultraviolet light or blue light.

Meanwhile, the wavelength conversion layer 25 covers the LED chip 23. Inan embodiment, after the LED chip 23 is mounted, the wavelengthconversion layer 25 may be formed by filling the cavity 21 a with amolding resin containing a phosphor. In this case, the upper surface ofthe wavelength conversion layer 25, which fills the cavity 21 a of thehousing 21, may be substantially flat or convex. Also, a molding resinhaving a lens shape may be further formed on the wavelength conversionlayer 25.

In another embodiment, the LED chip 23 with a conformal phosphor coatinglayer formed thereon may be mounted on the housing 21. In other words, aconformal phosphor coating layer may be applied on the LED chip 23, andthe LED chip 23 including the conformal phosphor coating layer may bemounted on the housing 21. The LED chip 23 including the conformalphosphor coating layer may be molded by a transparent resin. Inaddition, the molding resin may have a lens shape, and thus, the moldingresin may serve as a primary lens.

The wavelength conversion layer 25 converts a wavelength of lightemitted from the LED chip 23 to implement mixed color light, forexample, white light.

The light emitting device 20 is designed to have a light orientationdistribution of a mirror surface symmetry, and in particular, the lightemitting device 20 may be designed to have a light orientationdistribution of a rotational symmetry. In this case, an axis of thelight emitting device 20 directed toward the center of the lightorientation distribution is defined as an optical axis L. That is, thelight emitting device 20 is designed to have a light orientationdistribution that is bilaterally symmetrical with respect to the opticalaxis L. In general, the cavity 21 a of the housing 21 may be formed tohave a mirror surface symmetry, and the optical axis L may be defined asa straight line passing through the center of the cavity 21 a.

Referring back to FIG. 2, the lens 30 includes a lower surface 31 and anupper surface 35, and may further include a flange 37 and legs 39. Thelower surface 31 includes a concave portion 31 a, and the upper surface35 includes a concave surface 35 a and a convex surface 35 b.

The lower surface 31 is formed with a substantially disk-shaped flatsurface, and the concave portion 31 a is positioned in a central portionof the lower surface 31. The lower surface 31 may not be flat and may beformed with various uneven patterns.

Meanwhile, the inner surface of the concave portion 31 a has a lateralsurface 33 a and an upper end surface 33 b. The upper end surface 33 bis perpendicular to a central axis C, and the lateral surface 33 acontinuously extends from the upper end surface 33 b to the entrance ofthe concave portion 31 a. When the central axis C is aligned to beconsistent with the optical axis L of the light emitting device 20, thecentral axis C is defined as a central axis of the lens 30 as the centerof a light orientation distribution emitted from the lens 30.

The concave portion 31 a may be shaped such that the width is graduallynarrowed upward from the entrance thereof. That is, the lateral surface33 a becomes closer to the central axis C as it goes from the entranceto the upper end surface 33 b. Accordingly, the upper end surface 33 bregion may be formed to be relatively smaller than the entrance. Thelateral surface 33 a may have a relatively gentle slope in the vicinityof the upper end surface 33 b.

The upper end surface 33 b region is restricted to a region narrowerthan the entrance region of the concave portion 31 a. In addition, theupper end surface 33 b region may be restricted to a region narrowerthan a region surrounded by an inflection line formed by the concavesurface 35 a and the convex surface 35 b of the upper surface 35.Moreover, the upper end surface 33 b region may be restricted to bepositioned in a region narrower than the cavity 21 a region, i.e., alight exit region, of the light emitting device 20.

When the optical axis L of the light emitting device 20 and the centralaxis C of the lens 30 are misaligned, the upper end surface 33 b regionreduces a change in the light orientation distribution emitted throughthe upper surface 35 of the lens 30. Thus, the upper end surface 33 bregion may be minimized in consideration of an alignment error betweenthe light emitting device 20 and the lens 30.

Meanwhile, the upper surface 35 of the lens 30 includes the concavesurface 35 a and the convex surface 35 b continuously extending from theconcave surface 35 a with reference to the central axis C. A line wherethe concave surface 35 a and the convex surface 35 b meet each other isthe inflection line. The concave surface 35 a refracts light emitted inthe vicinity of the central axis C of the lens 30 at a relatively largeangle to disperse light in the vicinity of the central axis C. Also, theconvex surface 35 b increases an amount of light emitted outward fromthe central axis C.

The upper surface 35 and the concave portion 31 a are symmetrical withrespect to the central axis C. For example, the upper surface 35 and theconcave portion 31 a have a mirror surface symmetry with respect to asurface passing through the central axis C, or may have a rotator shapewith respect to the central axis C. Also, the concave portion 31 a andthe upper surface 35 may have various shapes according to a requiredlight orientation distribution.

Meanwhile, the flange 37 connects the upper surface 35 and the lowersurface 31 and limits an outer size of the lens 30. Uneven patterns maybe formed on a lateral surface of the flange 37 and the lower surface31. Meanwhile, the legs 39 of the lens 30 are connected to the PCB 10 tosupport the lower surface 31 such that the lower surface 31 is separatedfrom the PCB 10. For example, the connection may be performed such thata front end of each of the legs 39 is attached to the PCB 10 by anadhesive, or each of the legs 39 is inserted into a hole formed in thePCB 10.

The lens 30 is disposed to be spaced apart from the light emittingdevice 20. Therefore, air gap is formed within the concave portion 31 a.The housing 21 of the light emitting device 20 may be positioned underthe lower surface 31, and the wavelength conversion layer 25 of thelight emitting device 20 may be positioned under the lower surface 31and distant from the concave portion 31 a. Accordingly, it is possibleto prevent the loss of light travelling within the concave portion 31 adue to the absorption into the housing 21 or the wavelength conversionlayer 25.

According to the present embodiment, since the surface perpendicular tothe central axis C is formed within the concave portion 31 a, a changein the light orientation distribution emitted from the lens 30 can bereduced even when an alignment error occurs between the light emittingdevice 20 and the lens 30. In addition, since a relatively sharp apex isnot formed in the concave portion 31 a, the lens can be easilyfabricated.

FIG. 4 is cross-sectional views for describing various modifications ofthe lens. Various modifications of the concave portion 31 a in FIG. 2will be described.

In FIG. 4A, a portion of the upper end surface 33 b perpendicular to thecentral axis C described above with reference to FIG. 2 forms adownwardly convex surface in the vicinity of the central axis C. Lightincident to the vicinity of the central axis C can be primarilycontrolled by the convex surface.

FIG. 4B is similar to FIG. 4A but different in that the surface of theupper end surface 33 b in FIG. 4A, which is perpendicular to the centralaxis C, is formed to be upwardly concave. Since the upper end surface 33b mixedly has the upwardly concave surface and the downwardly convexsurface, a change in the light orientation distribution due to thealignment error between the light emitting device 20 and the lens 30 canbe reduced.

In FIG. 4C, a portion of the upper end surface 33 b perpendicular to thecentral axis C described above with reference to FIG. 2 forms anupwardly concave surface in the vicinity of the central axis C. Lightincident to the vicinity of the central axis C can be further dispersedby the concave surface.

FIG. 4D is similar to FIG. 4C but different in that the surface of theupper end surface 33 b in FIG. 4(a), which is perpendicular to thecentral axis C, is formed to be downwardly convex. Since the upper endsurface 33 b mixedly has the upwardly concave surface and the downwardlyconvex surface, a change in the light orientation distribution due tothe alignment error between the light emitting device 20 and the lens 30can be reduced.

FIG. 5 is lens cross-sectional views for describing a light emittingmodule according to another embodiment of the present invention.

Referring to FIG. 5A, a light scattering pattern 33 c may be formed onthe upper end surface 33 b. The light scattering pattern 33 c may beformed with an uneven pattern. In addition, a light scattering pattern35 c may also be formed on the concave surface 35 a. The lightscattering pattern 35 c may also be formed with an uneven pattern.

In general, a relatively large amount of luminous flux is concentratedon the vicinity of the central axis C of the lens 30. In addition, inthe embodiments of the present invention, since the upper end surface 33b is perpendicular to the central axis C, luminous flux may be furtherconcentrated on the vicinity of the central axis C. Thus, by forming thelight scattering patterns 33 c and 35 c on the upper end surface 33 band/or the concave surface 35 a, luminous flux in the vicinity of thecentral axis C may be distributed.

Referring to FIG. 5B, a material layer 39 a having a refractive indexdifferent from that of the lens 30 may be positioned on the upper endsurface 33 b. The material layer 39 a may have a refractive indexgreater than that of the lens, and thus, it may change a path of lightincident on the upper end surface 33 b.

In addition, a material layer 39 b having a refractive index from thatof the lens 30 may be positioned on the concave surface 35 a. Thematerial layer 39 b may have a refractive index greater than that of thelens, and thus, a refraction angle of light emitted through the concavesurface 35 a may become larger.

The light scattering patterns 33 c and 35 c in FIG. 5A and the materiallayers 39 a and 39 b in FIG. 5B may also be applied to various lensesillustrated in FIG. 4.

FIG. 6 is a cross-sectional view illustrating dimensions of the lightemitting module used in the simulation. Reference numerals of FIGS. 2and 3 will be used herein.

The cavity 21 a of the light emitting device 20 has a diameter of 2.1 mmand a height of 0.6 mm. The wavelength conversion layer 25 fills thecavity 21 a and has a flat surface. Meanwhile, a distance d between thelight emitting device 20 and the lower surface 31 of the lens 30 is 0.18mm, and the light emitting device 20 and the lens 30 are disposed suchthat the optical axis L and the central axis C are aligned.

Meanwhile, a height H of the lens 30 is 4.7 mm, and a width W1 of theupper surface 35 is 15 mm. A width W2 of the concave surface 35 a is 4.3mm. A width w1 of the entrance of the concave portion 31 a positioned inthe lower surface 31 is 2.3 mm, a width w2 of the upper end surface 33 bis 0.5 mm, and a height h of the concave portion 31 a is 1.8 mm.

FIG. 7 is graphs for describing shapes of the lens of FIG. 6. FIG. 7A isa cross-sectional view for describing a reference point P, a distance R,an incident angle θ1, and an exit angle θ5, and FIG. 7B shows a changein the distance R according to the incident angle θ1. FIG. 7C shows achange in θ5/θ1 according to the incident angle θ1. Meanwhile, FIG. 8illustrates light beam travelling directions when light beams areincident from the reference point P to the lens 30 at 3° intervals.

Referring to FIG. 7A, the reference point P indicates a light exit pointof the light emitting device 20 positioned on the optical axis L. Thereference point P may be appropriately determined to be positioned onthe outer surface of the wavelength conversion layer 25 in order toexclude influence of light scattering, or the like, by phosphors in thelight emitting device 20.

Meanwhile, θ1 is an angle at which light is incident from the referencepoint P to the lens 30, namely, an incident angle, and θ5 is an angle atwhich light is emitted from the upper surface 35 of the lens 30, namely,an exit angle. Meanwhile, R is a distance from the reference point P tothe inner surface of the concave portion 31 a.

Referring to FIG. 7B, since the upper end surface 33 b of the concaveportion 31 a is perpendicular to the central axis C, R is slightlyincreased as θ1 is increased. The enlarged graph illustrated in thegraph of FIG. 7B shows the increase of R. Meanwhile, as θ1 is increasedin the lateral surface 33 a of the concave portion 31 a, R is reducedand is slightly increased in the vicinity of the entrance of the concaveportion 31 a.

Referring to FIG. 7C, as θ1 is increased, (θ5/θ1) is sharply increasedin the vicinity of the concave surface 35 a and relatively gentlyreduced in the vicinity of the convex surface 35 b. In the presentembodiment, as illustrated in FIG. 8, luminous fluxes of light emittedin the vicinity where the concave surface 35 a and the convex surface 35b are adjacent may be overlapped with each other. Namely, a refractionangle of light, which is included in the light incident from thereference point P and emitted toward the concave surface 35 a, may begreater than that of light emitted toward the convex surface 35 b in thevicinity of the inflection line. Thus, concentration of luminous flux inthe vicinity of the central axis C can be lessened by controlling theshape of the concave surface 35 a and the convex surface 35 b whileallowing the upper end surface 33 b of the concave portion 31 a to havea flat shape.

FIG. 9 is graphs showing illuminance distributions based on the lightemitting device and the lens of FIG. 6. Specifically, FIG. 9A shows anilluminance distribution of the light emitting device, and FIG. 9B showsan illuminance distribution of the light emitting module using a lens.The illuminance distribution was represented by a magnitude of aluminous flux density of light incident on a screen spaced apart fromthe light emitting device by 25 mm.

As illustrated in FIG. 9A, the light emitting device 20 has anilluminance distribution that is bilaterally symmetrical with respect tothe optical axis C, in which the luminous flux density is very high inthe center and sharply reduced toward a peripheral portion. When thelens 30 is applied to the light emitting device 20, a generally uniformluminous density can be obtained within a radius of 40 mm as illustratedin FIG. 9B.

FIG. 10 is graphs showing light orientation distributions based on thelight emitting device and the lens of FIG. 6. Specifically, FIG. 10Ashows a light orientation distribution of a light emitting device, andFIG. 10B shows a light orientation distribution of a light emittingmodule using a lens. The light orientation distribution indicatesluminous intensity according to a viewing angle at a point spaced apartby 5 m from the reference point P, and orientation distribution inmutually perpendicular directions are indicated to overlap in the singlegraph.

As illustrated in FIG. 10A, light emitted from the light emitting device20 has a tendency that luminous intensity is high at 0°, i.e., at thecenter, and the luminous intensity is reduced as the viewing angle isincreased. In comparison, when a lens is applied, as illustrated in FIG.10B, luminous intensity is relatively low in the viewing angle 0° andrelatively high around 70°.

Thus, the light orientation distribution of the light emitting device,which is strong in the center, may be changed by applying the lens 30,to thereby uniformly backlight a relatively large area.

The light emitting module and the lens according to embodiments of thepresent invention may also be applied to a surface illuminationapparatus, without being limited to backlighting of a liquid crystaldisplay.

FIG. 11 is a view for describing a light pattern of a surface lightsource according to another embodiment of the present invention.

Referring to FIG. 11, according to other embodiments of the presentinvention, light orientation pattern Lp emitted through a lens has anelongated shape. Thus, a light pattern in which a bright portion Wp iselongated may be implemented by arranging the light orientation patternsLp at constant intervals.

Since the elongated light orientation patterns Lp are arranged, theformation of the dark portion B_(P) as in the related art can beprevented or minimized, and thus, the luminous flux distribution may beadjusted to remove the bright portion Wp without consideration of thedark portion B_(P), thereby easily implementing a uniform surface lightsource.

FIG. 12 is a schematic perspective view for describing a light emittingmodule according to an embodiment of the present invention. FIG. 13 iscross-sectional views of the light emitting module of FIG. 12.Specifically, FIG. 13A is a cross-sectional view taken in a direction ofa major axis (y), and FIG. 13B is a cross-sectional view taken in adirection of a minor axis (x).

Referring to FIGS. 12 and 13, the light emitting module includes a PCB10, a light emitting device 20, and a lens 30. Although the PCB 10 ispartially illustrated, a plurality of light emitting devices 20 may bevariously arranged in a straight-line or matrix form on the single PCB10.

Since the PCB 10 is the same as described above with reference to FIG.2, a detailed description thereof will be omitted. Since the lightemitting device 20 is also the same as described above with reference toFIG. 3, a detailed description thereof will be omitted. As describedabove with reference to FIG. 3, the wavelength conversion layer 25 maybe formed to cover the LED chip 23 by filling the cavity 21 a with amolding resin containing phosphors, or the LED chip with a conformalphosphor coating layer formed thereon may be mounted on the housing 21.

It has been described that the light emitting device 20 including theLED chip 23 and the housing 21 is mounted on the PCB 10, but the LEDchip 23 may be directly mounted on the PCB 10 and the wavelengthconversion layer 25 may cover the LED chip 23 on the PCB 10.

Referring back to FIGS. 13A and 13B, the lens 30 may include a lowersurface 31 and an upper surface 35, and also includes a flange 37 andlegs 39. The lower surface 31 includes the concave portion 31 a, and theupper surface 35 includes the concave surface 35 a and the convexsurface 35 b.

The lower surface 31 is formed with a substantially disk-shaped flatsurface, and the concave portion 31 a is positioned in a central portionof the lower surface 31. The lower surface 31 may not be flat and may beformed with various uneven patterns.

The concave portion 31 a is a portion in which light emitted from thelight emitting device 20 is incident on the lens 30. The LED chip 23 ispositioned under the central portion of the concave portion 31 a. Theentrance region of the concave portion 31 a has an elongated shape. Inthe drawing, the entrance region of the concave portion 31 a iselongated in the y-axis direction. In this case, the x-axis direction isa minor-axis direction and the y-axis direction is a major-axisdirection.

The entrance region of the concave portion 31 a may have various shapes.For example, as illustrated in FIG. 14, the entrance region of theconcave portion 31 a may have (a) a rectangular shape, (b) an ovalshape, (c) a rectangular shape with rounded corners, and so on. Here, awidth of the entrance region of the concave portion 31 a in themajor-axis direction is indicated as ‘a’ and a width thereof in theminor-axis direction is indicated as ‘b’.

Meanwhile, the width of the concave portion 31 a is narrowed as it goesfrom the entrance region to the interior of the concave portion 31 a. Asillustrated in FIGS. 15A and 15B, a cross-sectional shape of the concaveportion 31 a may be a trapezoid shape having bilateral symmetry. FIG.15A shows a cross section of the concave portion 31 a taken in themajor-axis (y) direction, and FIG. 15B shows a cross section of theconcave portion 31 a taken in the minor-axis (x) direction.

In FIG. 15A, a length of the bottom side of the trapezoid is indicatedas a1, a length of the top side thereof is indicated as a2, and an angleof a line passing through the edge of the top side from the center ofthe bottom side with respect to the central axis is indicated as α.Here, a2 is smaller than a1. Meanwhile, in FIG. 15B, a length of thebottom side of the trapezoid is indicated as b1, a length of the topside thereof is indicated as b2, and an angle of a line passing throughthe edge of the top side from the center of the bottom side with respectto the central axis is indicated as β. Here, b2 is smaller than b1. Inthis case, a2 is greater than b2, and thus, it is preferable that a isgreater than β.

The case where the cross-sectional shape of the concave portion 31 a isthe trapezoid shape in which the lateral surface is a straight line hasbeen described with reference to FIGS. 15A and 15B, but as illustratedin FIGS. 16A and 16B, the cross-sectional shape of the concave portion31 a may also be a trapezoid shape in which the lateral surface is acurved line.

By forming the entrance region of the concave portion 31 a in anelongated shape, an elongated light orientation pattern Lp asillustrated in FIG. 11 may be implemented.

Referring back to FIGS. 13A and 13B, the inner surface of the concaveportion 31 a may have the lateral surface 33 a and the upper end surface33 b. The upper end surface 33 b is perpendicular to the central axis C,and the lateral surface 33 a continuously extends from the upper endsurface 33 b to the entrance of the concave portion 31 a. When thecentral axis C is aligned to be consistent with the optical axis L ofthe light emitting device 20, the central axis C is defined as thecenter of a light orientation distribution emitted from the lens 30.

As described above, the concave portion 31 a may be shaped such that thewidth is gradually narrowed upward from the entrance thereof. That is,the lateral surface 33 a becomes closer to the central axis C as it goesfrom the entrance to the upper end surface 33 b. Accordingly, the upperend surface 33 b region may be formed to be relatively smaller than theentrance. The lateral surface 33 a may have a relatively gentle slope inthe vicinity of the upper end surface 33 b.

The upper end surface 33 b region is restricted to a region narrowerthan the entrance region of the concave portion 31 a. In particular, thewidth of the upper end surface 33 b in the minor-axis (x) direction maybe restricted to a region narrower than a region surrounded by aninflection line formed by the concave surface 35 a and the convexsurface 35 b of the upper surface 35. Moreover, the width of the upperend surface 33 b in the minor-axis (x) direction may be restricted to bepositioned in a region narrower than the cavity 21 a region, i.e., alight exit region, of the light emitting device 20.

When the optical axis L of the light emitting device 20 and the centralaxis C of the lens 30 are misaligned, the upper end surface 33 b regionreduces a change in the light orientation distribution emitted throughthe upper surface 35 of the lens 30. Thus, the upper end surface 33 bregion may be minimized in consideration of an alignment error betweenthe light emitting device 20 and the lens 30.

Meanwhile, the upper surface 35 of the lens 30 includes the concavesurface 35 a and the convex surface 35 b continued from the concavesurface 35 a with reference to the central axis C. A line where theconcave surface 35 a and the convex surface 35 b meet each other is aninflection line. The concave surface 35 a refracts light emitted in thevicinity of the central axis C of the lens 30 at a relatively largeangle to disperse light in the vicinity of the central axis C. Also, theconvex surface 35 b increases an amount of light emitted outward fromthe central axis C.

The upper surface 35 and the concave portion 31 a have a mirror surfacesymmetry with respect to the surface passing through the central axis Calong the x axis and the y axis. Also, the upper surface 35 may have arotator shape with respect to the central axis C. Also, the concaveportion 31 a and the upper surface 35 may have various shapes accordingto a required light orientation distribution.

Meanwhile, the flange 37 connects the upper surface 35 and the lowersurface 31 and limits an outer size of the lens 30. Uneven patterns 37 cmay be formed on a lateral surface of the flange 37 and the lowersurface 31. Meanwhile, the legs 39 of the lens 30 are connected to thePCB 10 to support the lower surface 31 such that the lower surface 31 isseparated from the PCB 10. For example, the connection may be performedsuch that a front end of each of the legs 39 is attached to the PCB 10by an adhesive, or each of the legs 39 is inserted into a hole formed inthe PCB 10.

The lens 30 is disposed to be spaced apart from the light emittingdevice 20. Therefore, air gap is formed within the concave portion 31 a.The housing 21 of the light emitting device 20 may be positioned underthe lower surface 31, and the wavelength conversion layer 25 of thelight emitting device 20 may be positioned under the lower surface 31and distant from the concave portion 31 a. Accordingly, it is possibleto prevent the loss of light travelling within the concave portion 31 adue to the absorption into the housing 21 or the wavelength conversionlayer 25.

According to the present embodiment, since the entrance region of theconcave portion 31 a is formed to have an elongated shape, the lightorientation pattern emitted through the lens 30 may have a shapeelongated in the minor-axis (x) direction. Also, since the surfaceperpendicular to the central axis C is formed within the concave portion31 a, a change in the light orientation distribution emitted from thelens 30 can be reduced even when an alignment error occurs between thelight emitting device 20 and the lens 30. In addition, since the upperend surface 33 b of the concave portion 31 a is formed as a flatsurface, a relatively sharp apex is not formed in the concave portion 31a. Therefore, the lens can be easily fabricated.

The concave portion 31 a having a trapezoid shape has been described,but the shape of the concave portion 31 a may be variously modifiedrather than being limited thereto. For example, as described above withreference to FIGS. 4A and 4B, the shape of the concave portion 31 a ofFIG. 13 may be variously deformed to primarily control light incident tothe vicinity of the central axis C to disperse light or alleviate achange in a light orientation distribution due to the alignment errorbetween the light emitting device and the lens.

FIG. 17 is a graph showing an example of a light orientationdistribution of a light emitting module using a lens according to anembodiment of the present invention. A light orientation distribution Pxin the x-axis direction, a light orientation distribution Py in they-axis direction, and a light orientation distribution P45 in a45-degree direction were simulated by using the light emitting device 20having the same illuminance distribution in the minor-axis (x) directionand the major-axis (y) direction and the lens 30 described above withreference to FIGS. 12 and 13. The light orientation distributionsindicate luminous intensities according to viewing angles at a pointdistant from the light emitting device 20 by 5 m, and orientationdistributions in the respective direction are shown to overlap in thesingle graph.

As illustrated in FIG. 17, the light orientation distribution Px in theminor-axis (x) direction has a relatively low luminous intensity at theviewing angle of 0° and a relatively high luminous intensity in thevicinity of 70°. This means that light is extensively distributed. Incomparison, the light orientation distribution P45 in the 45-degreedirection with respect to the light orientation distribution Py in themajor-axis (y) direction and the x axis has a luminous intensity that isnot greatly changed according to the viewing angle. Thus, it can be seenthat light is not extensively distributed.

Therefore, it can be seen that a light orientation pattern elongated inthe x-axis direction can be obtained by the light emitting module.

FIG. 18 is views for describing a lens according to another embodimentof the present invention. Specifically, FIG. 18 is a perspective viewand FIGS. 18B and 18C are cross-sectional-views taken in mutuallyperpendicular directions. In the following description, the samereference numerals as those of FIG. 13 will be used.

Referring to FIGS. 18A and 18B, the lens 30 according to the presentembodiment is similar to that described above with reference to FIGS. 12and 13, but has a difference in the shape of the upper surface 35. Thatis, the upper surface 35 of the lens 30 has a shape elongated in thedirection perpendicular to the major-axis (y) direction of the concaveportion 31 a, namely, in the minor-axis (x) direction of the concaveportion 31 a. In particular, the upper surface 35 of the lens 30 mayhave a shape in which two hemispheres overlap each other. A symmetricalsurface of the two hemispheres is consistent with a surface passingthrough the center of the concave portion 31 a in the major-axisdirection of the concave portion 31 a.

Since the upper surface 35 of the lens 30 has the elongated shape in theminor-axis direction of the concave portion 31 a, light can be dispersedby the shape of the upper surface 35 of the lens 30 together with theshape of the concave portion 31 a, light orientation pattern emittedfrom the lens 30 may be made to have a further elongated shape.

Meanwhile, in the foregoing embodiments, a light scattering pattern (notillustrated) may be formed in the upper end surface 33 b of the concaveportion 31 a. The light scattering pattern may be formed with an unevenpattern. In addition, a light scattering pattern, for example, an unevenpattern, may also be formed on the concave surface 35 a of the uppersurface 35. In general, a relatively large amount of luminous flux isconcentrated on the vicinity of the central axis C of the lens 30. Inaddition, in the embodiments of the present invention, since the upperend surface 33 b is substantially perpendicular to the central axis C,luminous flux may be further concentrated on the vicinity of the centralaxis C. Thus, by forming the light scattering patterns on the upper endsurface 33 b and/or the concave surface 35 a, luminous flux in thevicinity of the central axis C may be dispersed.

In addition, in order to disperse luminous flux in the vicinity of thecentral axis C, a material layer (not illustrated) having a refractiveindex different from that of the lens 30 may be positioned on the upperend surface 33 b. The material layer 39 a may have a refractive indexgreater than that of the lens, and thus, it may change a path of lightincident on the upper end surface 33 b. In addition, a material layer 39b having a refractive index from that of the lens 30 may be positionedon the concave surface 35 a. The material layer 39 b may have arefractive index greater than that of the lens, and thus, a refractionangle of light emitted through the concave surface 35 a may becomelarger.

FIG. 19 is a cross-sectional view for describing a light emitting modulehaving a plurality of light emitting devices according to an embodimentof the present invention.

Referring to FIG. 19, the light emitting module is similar to the lightemitting module described above with reference to FIGS. 12 and 13, buthas a difference in that a plurality of light emitting devices 20 aredisposed on the PCB 10. The lens 30 described above with reference toFIGS. 12 and 13 is disposed on each of the light emitting devices 20.

The light emitting device 20 may be arranged in a row on the PCB 10, ormay be arranged in various shapes, such as a matrix shape or a honeycombshape. Through the arrangement of the light emitting devices 20, thelight patterns as illustrated in FIG. 11 can be implemented. Inparticular, since the elongated light pattern Lp is implemented by thelens 30, the generation of the dark portion Bp as in the related art canbe eliminated or reduced. Therefore, the surface light source forillumination or the surface light source for backlighting, whichexhibits uniform luminous intensity over a large area can be provided.

While the present invention has been described with respect to thespecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

What is claimed is:
 1. A light emitting module, comprising: a housingcomprising a cavity; a light emitting device comprising a light emittingdiode chip disposed in the cavity; and a wavelength conversion layerwhich fills the cavity of the housing; and a lens comprising: a firstportion comprising a lower surface and a concave portion comprising anentrance region, the concave portion being enclosed by the lower surfaceand narrowing from the entrance region toward a direction of a centralaxis, which is perpendicular to the lower surface, a second portioncomprising a concave surface disposed on the central axis, and aplurality of legs supporting the lower surface, wherein the wavelengthconversion layer is disposed below the lower surface and is enclosed bythe housing, wherein the wavelength conversion layer overlaps a regionnarrower than the entrance region, and wherein at least a portion of thehousing is disposed outside of the entrance region.
 2. The lightemitting module of claim 1, wherein the concave portion comprises anupper end surface spaced apart from the lower surface.
 3. The lightemitting module of claim 2, wherein the upper end surface is flat. 4.The light emitting module of claim 3, a light scattering pattern isdisposed on the upper end surface.
 5. The light emitting module of claim3, wherein a material layer having a refractive index greater than thatof the lens is disposed on the upper end surface.
 6. The light emittingmodule of claim 2, wherein the upper end surface comprises a surfaceselected from the group consisting of a downwardly convex surface and anupwardly concave surface.
 7. The light emitting module of claim 2,wherein the upper end surface comprises a rounded surface.
 8. The lightemitting module of claim 2, wherein the second portion of the lensfurther comprises a convex surface connected to the concave surface. 9.The light emitting module of claim 8, wherein the lens further comprisesa flange connected to the convex surface of the second portion and thelower surface of the first portion.
 10. The light emitting module ofclaim 9, wherein an upper portion of the flange is disposed below theupper end surface.
 11. The light emitting module of claim 10, whereinthe flange comprises a vertical lateral surface.
 12. The light emittingmodule of claim 11, wherein the vertical lateral surface comprisesuneven patterns.
 13. The light emitting module of claim 11, wherein thevertical lateral surface is connected to the lower surface of the firstportion of the lens.
 14. The light emitting module of claim 11, whereinthe entrance region is elongated in one direction.
 15. The lightemitting module of claim 1, further comprising a printed circuit board,wherein the housing is disposed on the printed circuit board, andwherein the plurality of legs are connected to the printed circuitboard.
 16. The light emitting module of claim 15, wherein the printedcircuit board comprises an upper surface and a reflective film disposedon the upper surface of the printed circuit board.
 17. The lightemitting module of claim 1, wherein uneven patterns are formed on thelower surface of the first portion.